![]() ![]() This situation is a classic example of a deadlock. Neither task can proceed past this state and release the lock required by the other task. Then Task 2 continues up to the point where Mutex #1 needs to be acquired.Īt this point, Task 2 is waiting for Task 1 to release Mutex #1, while Task 1 is waiting for Task 2 to release Mutex #2. The execution switches to Task 2, which first acquires the lock Mutex #2.Task 1 acquires the lock Mutex #1 and continues up to the point where Mutex #2 needs to be acquired.The deadlock results when the following events occur in this sequence: The program freeze at execution traces back to a deadlock in the code. The important thing to note is that the sequence of lock acquisition is reversed in the two tasks. The write operations are protected with two mutual exclusion locks, Mutex #1 and Mutex #2, held in sequence. Suppose that two tasks, Task 1 and Task 2, write values to the shared resources, sharedVar1 and sharedVar2. Deadlocks occur when multiple tasks or threads cannot make progress because each task is waiting for a lock held by another task that is also stuck. When such a defect occurs, it can take a long time to reproduce the issue and even longer to identify the root cause and fix it.ĭeadlocks are one of the most subtle defects in this category. However, multithreaded programming is highly complex and introduces subtle defects such as data races and deadlocks. When you author software to simultaneously handle multiple tasks, you may use multithreaded programming-programs with constructs such as multiple entry points, interleaving of threads, and asynchronous interrupts.
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